The use of wireless communications is expanding. Although wireless communications are most commonly used in wide-area environments (e.g. cellular), the use of wireless communication is greatly expanding in local area indoor environments, such as a retail environment, a factory environment, a warehouse environment, etc. In addition, such wireless local area network (WLAN) communications can use a variety of different services, using different frequency bands and communication protocols, e.g. Bluetooth™, IEEE 802.11 or Wi-Fi™, etc.
Within such indoor environments it is desirable to locate objects therein wirelessly using one of these communication networks. For example, in a retail environment it may be desirable to locate a customer for directed advertising, or in a warehouse it may be desirable to locate employees for performing a specific task.
One technique to provide locationing is to utilize Global Positioning System (GPS) receivers. However, such a solution is quite expensive, and is not practical for smaller networks, such as in a home or work environment. Moreover, such networks are usually installed indoors, where GPS receivers may not work properly.
Another technique to provide locationing is to utilize the timing of communication signals received by different receivers within the environment. For example, by examining the TDOA (Time Difference of Arrival) of signals from a transmitter by various receiving points, trilateration techniques to locate a mobile device. However, working out the exact arrival time of a wireless packet to nanosecond accuracy is difficult. Such techniques require precision timing measurements and infrastructure, with highly stable clocks and synchronization between receivers, which may not be available or may be cost prohibitive for smaller home/work environments.
Thus, there exists a need in the field of the present invention to provide sufficient locationing accuracy while being less demanding of clock stability and synchronization between different receivers.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.